1. Field of the Invention
The present invention relates to a powdered metal spray coating material which provides a good spray coating property to the base matel as well as excellent durability and heat and wear resistances, and capable of improving the spray coating property of a ceramic layer which will be subsequently formed thereon by spray coating, and to a process for producing such a material and the use thereof.
2. Description of the Prior Art
There is a known continuously casting mold which has a Ni-plated layer formed on an inner surface thereof, and a Co-Mo-Cr alloy layer formed thereonto by spray coating and consisting of 45 to 65% by weight of Co, 20 to 40% by weight of Mo and the balance of Cr, as disclosed in Japanese Patent Publication No. 5819/86. When this continuously casting mold is used as a mold for common discontinuously casting processes, a disadvantage is encountered that a blown or rugged portion may be produced, resulting in a degraded surface of a molded product, because a gas cannot be sufficiently removed during casting.
The present inventors have proposed, in Japanese Patent Application No. 46621/89, that after spray coating of a metal, a porous Al.sub.2 O.sub.3 /ZrO.sub.2 ceramic layer is provided on such coating layer by spray coating for the purpose of solving the above disadvantage.
However, there is a disadvantage of a very poor spray coating deposition of the ceramic layer onto the above prior art alloy layer. Further, the alloy layer has only still unsatisfactory wear and heat resistances and hence, a spray coating material having such properties improved has been desired.
Further, a spray coating material represented by "NiCoCrAlY" is disclosed in Hiromitsu Takeda, "Ceramic Coating", 195-205 (Sep. 30, 1988) issued by Dairy Industrial Press, Co., Corp. This spray coating material consists of Ni, Co, Cr, Al and Y and has a composition comprising 25% by weight of Co, 13% by weight of Al, 17% by weight of Cr, 0.45% by weight of Y and the balance of Ni. The spray coating material undoubtedly has an excellent spray coating property and provides an excellent deposition of a ceramic spray coating and excellent heat and wear resistances, but suffers from a disadvantage that when the material after spray-coating comes into contact with the melt of magnesium or a magenesium alloy, or aluminum or an aluminum alloy, e.g., when a molded product of such a metal is produced using a mold, aluminum itself in the spray coating material may be deposited on a molded product, and/or aluminum or magnesium itself in the molded product may be adhered to a spray-coated substrate or mold blank.